1. Field of the Invention
The present invention relates to a people counting device which performs image recognition of persons in a monitor camera and grasps the number of the persons by the image recognition, and a people trajectory analysis device capable of analyzing a trajectory of a person.
2. Description of Related Art
There is an increasing need for a system for realizing safety management or traffic census in commercial facilities or public facilities by using information of the number of persons present in a detection region obtained by image recognition from an image of a camera. For example, a typical example of this system using the information of the number of persons is a tailgating detection system for determining whether or not there is an accompanied person before individual authentication in a room entry/exit system, or a person detection system for determining whether or not there is a person in an off-limits place. These systems are for a state in which the number of persons in the detection region is relatively small. A crowded degree estimation system for estimating a crowded degree by counting the rough number of persons is also a typical example of the system using the information of the number of persons. This system is for a state in which the number of persons in the detection region is large. That is, the people counting for the quiet state is required to have high accuracy, while the people counting for the crowded state is not required to have high accuracy as compared with the quiet state.
In order to increase the effectiveness of the people counting system and to reduce the cost, one camera and one signal processing device are required to cover both the quiet time and the crowded time.
JP-A-2011-86045 (Patent Literature 1) discloses that in order to remove the influence of overlap between persons, a special camera is set just above persons, and people counting is realized by counting the number of heads of the persons in a detection region previously set in an image.
However, such a camera is usually dedicated for people counting, and the cost becomes high. Thus, a people counting technique using an image of a general monitor camera is required.
In a people counting technique using a monitor camera image, similarly to the dedicated camera, a head which is relatively easy to be detected in a human body is usually detected in order to detect a person in the image. However, since the monitor camera is installed while the depression angle is obliquely downward, a head position and a foot position on the floor are different between a camera image coordinate system and a real world coordinate system. Thus, it is necessary to take consistency between the detected head position and the detection region set in the image. Thus, in the people counting technique using the image of the monitor camera, after the foot position is estimated from the head position of a person in the image, it is determined whether or not the foot position exists in the set detection region, and the people counting is realized by counting the number of feet which are determined to exist in the detection region.
JP-A-2001-056853 (Patent Literature 2) discloses a technique for estimating a foot position from a head position of a person in an image, in which the foot position is estimate by taking consistency between a lower end of a region, which appears to be a human body, detected from the image by background subtraction and the detected head position.
Besides, there is also a technique in which a head position in a three-dimensional space is derived from a head position on an image detected by geometric conversion, a position just below that by an average height is assumed to be a foot position in the three-dimensional space, and a foot position on the image is estimated by again using the geometrical conversion.
According to Non Patent Literature 1 (Toshizo Ogawa, Hironobu Fujiyoshi, “Tracking Camera System by Master-Slave Corresponding to Real Space”, Ninth Image Sensing Symposium, P. 211-216, June, 2003), a rough foot position can be estimated in a crowded state in which overlap between persons constantly occurs.
According to the technique of Patent Literature 2, in the quiet state in which the frequency of overlap between persons is low, the foot position can be accurately estimated without being influenced by a difference between the heights of the persons or postures. However, in the crowded state in which overlap between persons constantly occurs, there is a problem that a region which appears to be a human body detected by the background subtraction becomes giant by combination of plural persons, and the estimated foot position is significantly different from a true value.
According to the technique of Non Patent Literature 1, also in the quiet state in which the frequency of overlap between persons is low, the foot position is estimated by using the average height. Thus, the foot position of a person, such as a child, much different from the standard body type or a person sitting in the detection region is significantly different from the true value, and there is a problem that the accuracy of the foot estimation is low as compared with the technique of Patent Literature 2.